I've commented before so if I repeat myself I apologise - few points I would like to add to the discussion though:
In Elizabeth's defence one moment she was happily married, with two small daughters and a devoted husband and family, the next she is Queen Consort with a husband who is petrified he isn't up to the job - I think it is perhaps forgiveable that she found it hard to be charitable to the woman who in her view caused it all.
Now don't get me wrong i tend to agree with a certain courtier about the Duchess of York - "My reading of history is that she was quite happy as Duchess of York etc.....that doesn't mean to say she wouldn't want NOT to be Queen now."
Elizabeth was pretty much a typical example of a woman of her time, her class and her upbringing - as the first commoner to marry into the British Royal Family since Anne Hyde she was perhaps as Eleanor Roosevelt commented a bit "self-conciously regal" or as one politician put it a very conservative woman from a "pretty reactionary stable".
She was also popular, had a very mixed circle of friends and tended to be loyal to them.
During the early years of her marriage she was close to the Duke of Windsor and aware of the constraints put upon him and the difficulties he had with his parents in particular his father George V (as atttested to in some surviving letters from her to him).
I think it is common to suggest that Elizabeth was the power in the marriage whilst i think her influence and support were essential to the King - I don't think it is natural to read that she dictated attitudes to the Windsors - in fact the King's most recent biographers have been pretty clear that his views (particular in relation to the HRH) were very much his own. Even when the legal advice he received as King was contrary to his own insincts.
A number of recent biographers have also indicated that her longevity, popularity and strength have tended to downplay how reliant on her husband she was.
As Duke and Duchess of York, George and Elizabeth got on very well with the then Prince of Wales and certainly accepted and spent time with both Freda Dudley Ward (who Elizabeth once commented must be a most remarkable woman for certain things not to have happened) and with Lady Furness (who herself in her own biography was quite complimentary to the then Queen Mother perhaps unsurprisingly).
Wallis was different and I think to be fair the whole Royal Family felt the change quite deeply (particularly the Yorks and the Kents) - the Prince's behaviour changed and the things about Wallis that charmed him (her candour, humour, and the way she treated him as just a man rather than as some kind of demi-god) were the things that most puzzled and embarrassed his relations (and many others in his circle). But his determination to marry her was the key to the reaction of his family.
As is often the case the family chose to blame the cause, Wallis, rather than the person who was really to blame, Edward.
I don't know when Wallis and Edward began their derogatory comments about the Duchess of York - I suspect it was after his accession when there were some very uncomfortable moments - but to be fair by then Edward had reduced the time he saw his brothers and their families to the bare minimum (the Kents who had been very close to him felt it rather keenly) everything including his Royal duties came second to his all-consuming passion for Wallis.
The infamous meeting at Balmoral (as featured in the Kings Speech and in numerous biographers) is debated as whether it happened.
Certainly those comments became cattier and more unpleasant as time continued. On the other side we know Elizabeth enjoyed derogatory comments about Wallis (Joseph Kennedy's comment whilst at dinner at Windsor, the Queen's reference to "that woman" for example).
She certainly was infuriated by what she saw as attempts to brow-beat the King with constant telephone calls from Austria and then France and the Duke's high profile visits and trips and speeches which to be fair horrified the government, the court aswell as the Royal Family..
To be fair to Edward he wasn't used to having time on his hands nor to being ignored and not able to have it all his own way...he tended in conversation to continue to treat his younger brother as a younger brother rather than his sovereign which increasingly frustrated and irritated both sides.
His own lies about his financial position didn't help relations between the brothers which went quite frankly from bad to worse.